Helm, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

154
FXUS66 KMFR 221205
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
405 AM PST Sat Feb 22 2025

.DISCUSSION...It is a quiet morning, with high clouds streaming
aloft, and scattered areas of fog in valleys around the region.
Just offshore, however, lurks the first of several systems that
will pass through the region over the next several days.

The leading edge of an atmospheric river(AR) will arrive at the
southern Oregon and northern California coastline by mid day
today. This plume of warm moist air will raise snow levels up to
7000 feet by this evening and bring widespread wetting rain to
the region. Precipitation rates really pick up this evening into
Sunday morning as model guidance is showing rain rates of about
1.5-2" over 6 hours around Curry County.

Model values of integrated water vapor transport(IVT), a measure
of moisture flow, is also on the stronger side, around 500 to 750
for about 24 hours. Ensemble situational awareness tools suggest
these IVT values lie in the 98th percent for this time of year,
which is notable and suggest a strong AR. The other thing that
stands out is how much moisture is in the air. Precipitable water
is anticipated to reach 1 inch by tonight. This would lie in the
99th percentile for this time of year based on sounding
climatology for SPC and ensemble situation awareness tool. Our
record values are right around 1.2 inches. Needless to say, this
will be a very wet system for our area.

Between Sunday into Monday, another upper level disturbance in
this AR event will swing through region pushing the bulk of the
precipitation farther north, although we`ll still see rain
accumulate through Monday morning.

The flooding risk is still expected to be minor/limited as this
AR hits the region. Main stem rivers and streams will rise
rapidly through Sunday, although none of the rivers are
anticipated to reach action stage or minor flood. The one concern
that we do have is snow melt east of the Cascades in south central
Klamath and Lake Counties. That area got the brunt of snowfall
from the event a few weeks ago. However, not much rain is
anticipated to fall east of the Cascades. Plus, overnight lows
will fall very close to freezing east of the Cascades, so the
contribution of snowmelt overnight will be very limited. However,
there have been events in the past of some small stream flooding
east of the Cascades due to snow melt, so it`s just something to
watch out for.

Heading into Monday, models are now starting to resolve a quick-
hitting negatively tilted trough sweeping through the region.
At the surface, we now expect to see a rapidly deepening surface
low passing within 130W, and tight sea level pressure gradients
along the coast (from -8 to -10mb between NOrth Bend and Arcata).
These are all the ingredients we typically look for in a strong
wind event. A quick look at Ensemble tools shows significant wind
speed concerns, from sustained multi-level winds around the 95th
percentile in the NAEFS, and ECMWF extreme forecast index of
between 0.8 and 0.9 in surface winds, confidence is very high for
strong winds along the coast. Inland, gradients are still strong,
but due to the trajectory of the surface low, mid-level winds are
weaker and not as well aligned with the terrain. Despite this,
strong winds re still expected for the typical trouble spots:
the Shasta Valley, southern Rogue Valley, and much of the East
Side, especially in the Summer Lake area. High Wind Watches have
been issued for these areas, and details can be found at
PDXNPWMFR. Various Wind Advisories may be necessary as well, but
will wait on a few more model cycles before upgrading/issuing
further headlines.

Interestingly enough, winds will be the primary concern with this
system, as precipitation will be much lighter than the previous
systems, and snow levels are expected to remain well above 5000
feet.

Tuesday evening will be the end of this AR event with high
pressure building over the area. This quiet weather will persist
into Wednesday with temperatures continuing to remain on the
warmer side. Highs will be pushing the mid 60`s west of the
Cascades with some upper 60`s in the river valleys closer to the
coast. Temps will be a bit cooler east of the Cascades on
Wednesday with highs in the mid 50`s. A low chance of rain returns
on Thursday as an upper level wave quickly swings through the
region. -BPN/Smith


&&

.AVIATION...22/12Z TAFs...Widespread VFR prevails early this morning
with a mid-level cloud deck moving in from the Cascades west. Patchy
MVFR fog (visibility) has been in and out at Klamath Falls.
Amendments may be necessary at KLMT this morning since a fog bank
appears to be developing on satellite south of the airport. Some
uncertainty exists on whether or not it will completely settle in
over the airfield though.

This afternoon and tonight, light rain and MVFR ceilings/vis will
overspread the area from west to east as a frontal system offshore
moves in. Gusty south winds will develop at the coast at North Bend,
perhaps up to ~30kt. This should, for the most part, preclude low-
level wind shear (LLWS) there, but suppose it`s possible if the wind
dies down at the surface at times. However, there is a higher
probability of LLWS at RBG, MFR and LMT since surface winds in those
locations are probably a bit lower. -Spilde

&&

.MARINE...Updated 245 AM PST Saturday, February 22, 2025...An active
weather pattern will cause very hazardous conditions this weekend
into next week. South winds and steep seas will bring conditions
hazardous to small craft this morning. Then, winds increase to gales
this afternoon and persist into Sunday with very steep, hazardous
seas, highest near and north of Cape Blanco. Since a coastal jet
could form near Cape Blanco, the area of gales could expand south of
the Cape. For this reason, we`ve included all zones in the gale
warning. Another strong front will move through Monday with strong
gales and possible storm force wind gusts with very high and very
steep seas. Very steep seas persist into Tuesday, then things should
calm down from Wednesday onward. The front on Monday looks stronger
in the latest guidance, with solid gales and possible storm force
gusts (>=55 kt), so we have added a storm watch. This front will
build dangerous seas of 20-28 ft from Gold Beach northward, with
seas peaking at 16-20 ft south of there. -Spilde


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Watch from Monday morning through Monday evening for
     ORZ021-022-030-031.

CA...High Wind Watch from Monday morning through Monday evening for
     CAZ081-085.

PACIFIC COASTAL WATERS...Small Craft Advisory until 10 AM PST this
     morning for PZZ350-356-370-376.

     Gale Warning from 10 AM this morning to 4 PM PST Sunday for
     PZZ350-356-370-376.

     Storm Watch from late Sunday night through Monday evening for
     PZZ350-356-370-376.

&&

$$